Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a densidade quando simplificado mostra 南山区?
 ###Tabelas: CREATE TABLE basins (basins_id AUTO_INCREMENT PRIMARY KEY, Basin VARCHAR, Continent VARCHAR, Drains to VARCHAR, Basin Area km 2 INT, Basin Area mi 2 VARCHAR) CREATE TABLE subdivisions (subdivisions_id AUTO_INCREMENT PRIMARY KEY, English Name VARCHAR, Simplified VARCHAR, Traditional VARCHAR, Pinyin VARCHAR, Area VARCHAR, Population VARCHAR, Density VARCHAR) CREATE TABLE men's_doubles (men's_doubles_id AUTO_INCREMENT PRIMARY KEY, Location VARCHAR, Year INT, Champion VARCHAR, Runner-up VARCHAR, Score VARCHAR) CREATE TABLE belfast_and_northern_counties_railway_1848–1903__&__northern_counties_committee_1903–1949 (belfast_and_northern_counties_railway_1848–1903__&__northern_counties_committee_1903–1949_id AUTO_INCREMENT PRIMARY KEY, Class VARCHAR, Type VARCHAR, Fleet numbers VARCHAR, Quantity made INT, Manufacturer VARCHAR, Date made VARCHAR, Date withdrawn VARCHAR) CREATE TABLE per_competition (per_competition_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, League INT, Title Playoff INT, Super Cup INT, Total INT)  
SELECT Density FROM subdivisions WHERE Simplified = 南山区